Equipment based on suction gripping devices is used for this purpose, for gripping the upper surface of the uppermost veneer sheet in the stack and lifting the sheet, as for instance into contact with further transferring devices. The transferring devices may be horizontal rolls cooperating with the suction gripping devices, having rotating motion parallel to the intended transfer direction. The sheets to be transferred are lifted one by one with the suction gripping devices from the top of the stack into contact with the mantle surface of the rolls, and kept in contact with the mantle surface of the rolls for providing the transferring event. Another way is to pick up the topmost sheet with the suction gripping devices and transfer it onto a conveyor, as for instance a belt conveyor.
The suction gripping devices consist in principle of single suction nozzles arranged in one or several rows extending substantially over the stack. The devices operate without problems with full-sized veneer sheets, but problems are caused by random veneer layers consisting of narrower sheets than the sheets with full width.
It has been tried to compile these random sheet layers so, that the random width sheets are side by side in the layer and cover substantially the same area in the stack as the sheet with full width. At this kind of a stack layer, the transferring devices known in the art in general still operate without problems, in other words, the suction gripping devices get a grip on all sheets of the uppermost layer, and they are moved together from the stack forward, usually to the drying apparatus of veneer.
In spite of careful compiling of the layers in the stack, whether made manually or by machine, there are mistakes occurring when compiling the layers, as a result of which there can be sheets in a layer more or less overlapping each other. Overlapping sheets are also forwarded, when uppermost on the stack, supported by the suction gripping devices, at least partly overlapping. A part of the sheets taken along with the suction gripping devices may loosen too early, and fall back onto the stack, as a result of which the top layer of the stack will be mixed. Due to the overlapping, the veneer sheets that hold on cause problems for the apparatus handling the veneers in the next step, like in the drier, as blockages that are difficult to unblock, incomplete drying etc. A single random veneer left or fallen in the stack follows on top of the next full veneer in the next lifting step causing the overlapping problem.
With the apparatus of the present invention, these problems have been significantly solved.